/Engine/Source/Runtime/SlateCore/Public/Layout/BasicLayoutWidgetSlot.h
MoveTemp will cast a reference to an rvalue reference. This is UE's equivalent of std::move except that it will not compile when passed an rvalue or const object, because we would prefer to be informed when MoveTemp will have no effect.
TAlignmentWidgetSlotMixin ( SlotOwner, MoveTemp([InArgs](API\Runtime\SlateCore\Layout\TBasicLayoutWidgetSlot\InArgs)) )